A meringue is simply a mixture of stiffly whipped egg whites and sugar. When baked, it is very light, sweet and usually crisp.
There are 3 methods of preparing meringue batters, depending on how sugar is incorporated – French, Italian and Swiss.
French (or “ordinary”) meringue – sugar is beaten into the whipped whites. We use French meringue to make individual-serving-size desserts, decorations, rounds for layers in gateaux (pronounced ga-to = layer cakes) and shells that are filled with ice-cream or whipped cream and fruits to become vacherins (classic desserts). We also make French meringue as part of the preparation of separated egg sponge cake batters.
Italian meringue – hot sugar syrup is used instead of dry sugar. Used for some decorations and individual-serving-size desserts and as part of the preparation of vacherins shells and as a frosting on some gateaux.
Swiss meringue – egg whites and sugar are combined at the outset and whipped over low heat. Much heavier than French and Italian meringues and is used very little in modern cake making.
Adapted from The Art of the Cake: Modern French Baking and Decoration by Bruce Healy and Paul Bugat.